I juss bought a car. The guy upgraded the stock system with a Sony CDX-454RF changer, some sony cassette deck and some better speakers. I bought the pioneer deh-p7400mp a while back and wanna put it in my car but for some reason, I'm thinking the cd changer and this pioneer deck won't work together? I don't know much about changers but it says it uses the FM attenna? Can someone explain to me why I can or cannot use the pioneer deck? Thanks.